Field of the Invention
The invention relates to a method and a device for tracking the content of a movable fluid tank.
Fluid is understood as a liquid body, a gaseous body or a two-phase body of liquid and gas. For example, it can be an industrial gas (nitrogen, oxygen, argon, hydrogen, etc.) or a medical gas (oxygen among others). Depending on its use, this fluid is stored in a suitable tank, which can be connected to a device that uses the fluid in question. In the medical field, this device can include all means permitting administration of a gas to a patient.
A problem that arises is to know the amount of fluid contained in the tank, for example in order to anticipate the replacement thereof, or to know if there is a sufficient amount of fluid in a tank for a given application. In other words, the problem is that of establishing the autonomy of a movable tank.
Related Art
This problem is generally solved by directly measuring the amount of fluid in the tank. For example, the document WO-A-2005/093377 describes a display on the tank showing its remaining autonomy evaluated by a measurement of the internal pressure of the tank by a manometer. This solution has several disadvantages: cost of the measuring device, increased risk of leakage, which may pose a safety problem if the fluid is dangerous (for example toxic or inflammable), imprecision in the case of an evaluation of the amount by pressure measurement, lack of legibility of the result, and the bulk created by the cabling or the necessary pipes.
The document WO-A-2008/056082 describes, for its part, a medical device for gas insufflation comprising a gas outlet circuit, a connector for connecting a pressurized container in which the gas is stored, a pressure relief valve placed between the connector and the gas outlet circuit, a high-pressure sensor placed between the connector and the pressure relief valve, a flow meter placed at the outlet of the pressure relief valve. The volume of gas remaining after pressure relief is evaluated by means of the sensor and the flow meter during a release of the gas. This device also has several disadvantages. It requires pressure measurement upstream from the pressure relief valve, with the risks of leakage that this entails. It is necessary for the tank to be connected and for use of the fluid to take place in order to be able to deduce the residual content of the tank (if the latter is not connected, this determination is impossible by the method described). Finally, the method does not work if the content of the tank is in two phases, since there is then an additional degree of freedom, the amount of liquid present in the tank, that is not measured.